As SC53 noted, a well implemented subwoofer usually does not need to be set at high gain and/or high crossover frequency. This is particularly true when music, and not home theater special effects, is a priority.
Multiple subwoofers are used to get a more even bass response, it is NOT generally utilized to get more bass. This issue was discussed extensively in this forum a few days ago; see:
http://forum.audiogon.com/cgi-bin/fr.pl?bhome&1398310409&openfrom&1&4#1
You don't "need" two, but the results are usually better with two or more.
Multiple subwoofers are used to get a more even bass response, it is NOT generally utilized to get more bass. This issue was discussed extensively in this forum a few days ago; see:
http://forum.audiogon.com/cgi-bin/fr.pl?bhome&1398310409&openfrom&1&4#1
You don't "need" two, but the results are usually better with two or more.